DESCRIPTION (Applicant's abstract reproduced verbatim): Circadian clocks are located in the nervous system of all animal species and regulate the temporal expression of physiological, behavioral, and molecular processes. In this proposal, consideration is given to a Drosophila mutant called lark that identifies a clock output component controlling a behavioral event known as adult eclosion. The lark gene has been cloned, and the predicted amino acid sequence of the encoded product shows similarity to RNA-binding proteins of the RNA Recognition Motif (RRM) class, which are known to function in RNA transport, RNA splicing, or translational control. Lark protein abundance exhibits circadian oscillations in the cytoplasm of a population of neurosecretory cells which express CCAP, an insect neuropeptide implicated in the regulation of eclosion. These results suggest that lark controls the temporal gating of eclosion by regulating the translation or stability of target RNAs within the CCAP neurons. The proposed studies are designed to define the functional domains of lark, its potential role as an RNA-binding protein. and the mRNA targets relevant for the regulation of adult eclosion.